Videoconferences can involve transmission of video, audio, and other types of information between two or more videoconference locations, or between two or more videoconference participants. Generally, a videoconferencing endpoint at each participant's location will include one or more cameras for capturing images of the local participant and one or more display devices for displaying images of remote participants. The videoconferencing endpoint can also include one or more additional display devices for displaying digital content. When more than two endpoints participate in a videoconferencing session, a multipoint control unit (MCU) can be used as a conference controlling entity. The MCU and endpoints typically communicate over a communication network, with the MCU receiving and transmitting video, audio, and data channels from and to the endpoints.
In videoconferencing (and in other applications where images of people are taken or recorded), faces are often too dark in comparison to other regions in images. Unwanted darker regions can occur when a person faces away from a window, lamp, or other bright light source, while the camera collects image data of both the person and the light source. In this situation, a camera device can attempt to compensate for the brightness of the light source by using a small aperture or a short exposure (or both). The smaller aperture or shorter exposure time can in turn cause the face region to be underexposed, and thus comparatively dark, sometimes to the point that the face region is barely recognizable.
There have been attempts to correct these problems, none of which is completely satisfactory. A partial solution is to increase the exposure time for the camera. This technique has been used in a variety of applications, including videoconferencing systems, web cameras, digital video and still image cameras. This solution is, however, frequently inadequate. For example, some web cameras do not allow external software (such as that running on a personal computer or videoconferencing system) to control their exposure settings. Moreover, even when the camera is able to increase exposure time, this can cause an image to be partially washed-out. That is, while collecting more light may make a face region visible, it can cause the remainder of a region to be too bright, even to the point of making it non-visible. Thus, there is room for improvement in the art.